Li deinsertion mechanism and Jahn–Teller distortion in LiFe_0.75Mn_0.25PO₄: an operando x-ray absorption spectroscopy investigation

The electrochemical lithiation of the mixed metal olivine LiFe_0.75Mn_0.25PO₄ was followed by operando x-ray absorption spectroscopy (XAS) at both Fe and Mn K edges. XAS data were interpreted using an innovating chemometric approach, allowing the detailed reconstruction of the rather complicated reaction mechanism involving two different metal centres. In this way it was possible to precisely describe the Jahn–Teller effect occurring upon oxidation of the manganese centres. The thorough comprehension of the electrochemical mechanism is of high interest for studying the effect of lithium extraction in the olivine structure in the presence of Mn, which is known to partially hamper the complete lithiation of such mixed metal systems. (paper)